Some of the 267 asylum seekers Australia wants to deport to an offshore immigration center following a court ruling are suffering from cancer and other terminal illnesses, a senior government official said on Monday.
Australia's High Court last week upheld the government's right to deport detained asylum seekers to the tiny South Pacific island of Nauru, about 3,000 km (1,800 miles) northeast of Australia.
The decision provoked criticism from the United Nations and sparked protest, with churchleaders offering asylum seekers sanctuary.
The center has been widely criticized for harsh conditions and reports of systemic child abuse and sexual assault.
Some deportations could begin within days, but others would have to be dealt with in a staged fashion, because of the illnesses, said Michael Pezzullo, secretary of the department of immigration and border protection.
"In some cases we're talking about cancer, we're talking about all sorts of long-run illnesses," he told a parliamentary hearing.
"Regrettably in some cases, for reasons to do with very long-term, and indeed potentially terminal illnesses, some folks, I suspect, will be here for quite a while."
The refugees, including 37 babies, had been brought to Australia from Nauru for medical treatment.
Under Australia's controversial immigration policy, asylum seekers trying to reach the country by boat are intercepted and sent to camps on Nauru or on Manus island in Papua New Guinea. They can never be resettled in Australia.
Both the ruling conservative Liberal Party of Prime Minister Malcolm Turnbull and center-left Labor Party support the policy, which was introduced by former Labor Prime Minister Kevin Ruddy.
Both sides argue that the policy of deterrence is necessary to stop asylum seekers dying at sea while attempting to make the sea crossing on often rickety boats used by people smugglers.
The numbers trying to reach Australia are small in comparison with the floods of asylum seekers in Europe, the issue is a perennial hot-button political issue both at home and abroad.
On Monday Australia announced the appointment of veteran politician Philip Ruddock as its first special envoy for human rights.
"Australia has a strong record of promoting and protecting human rights, at home and around the world," Foreign Minister Julie Bishop said in a statement.
"Mr Ruddock will be reflecting the government's commitment to further strengthening Australia's contribution to advancing human rights."